It's a part of the last chirp of the Steam platform.
PC gaming isn't exactly an increasing market segment. Most PC's sold today are roughly 400-500 dollar netbooks or ultrabooks who can't play games worth a rats tail with their integrated graphics cards. At the same time, gaming is thriving on ever-increasing post-PC world of tablets, smart phones and home consoles – areas where Steam is virtually non-existant. Microsoft and Apple now ship app stores with their operating systems which cut out middle-men like Steam.
Think it's any coincidence that they put Steam on to Linux? And Mac a couple of years ago? And investigating building their own console and implementing Big Screen Mode? And now apps? They're doing everything they can, looking to exhaust every possible option to expand the market for Steam and tie people into purchasing their software on it. But it's got its limits. I don't think there's much they can do to thwart all the trends which are pointing against them. This is the beginning of the end.
Even if Steam starts to slumber and ferment, decreasing whatever source of additional revenue that lets the company stay afloat, Valve still have their gaming intellectual property to lean on.